There are several ways you can go. 1. You can use aluminum wedge bonding with immersion gold on the whole board. The one thing to be careful is to limit the amount of heat that the board sees. You can usually get several reflow profiles (>3) before the nickel can diffuse through the gold resulting in wire bonding difficulties. I did see a paper in a very recent IMAPS journal concerning gold ball bonding to immersion gold, so gold bonding may be possible on the immersion gold surface, but aluminum wedge bonding is more common I think. 2. You can use (thick) wire bondable gold (~30 micro inches) on the whole board. Solder embrittlement is the worry here. If you can have enough solder in the joint and control your reflow profiles, this may work. 3. I have seen palladium metallizations used. Sometimes immersion gold is plated over the palladium to give a nice solderable and wire bondable surface. 4. You can get selective gold plating (immersion on solderable pads, soft gold on the rest). This would involve another masking operation, and is usually more expensive, but sometimes the cost is justified. I'm sure there are a number of other ways to tackle this design. These are just the ones that I am familiar with. I would recommend staying away from HASL or fused solder. Any contamination from these metals on the wire bond pads make wire bonding difficult. Besides, you need a precious metal metallization anyway for the wire bonding, so why complicate the board by adding additional steps? I've been reading the heated debate with regard to the Surface Finishes Conference. I think that this may be an application where HASL or silver may not be the best option. If one is building boards like this one, the discussion at the Surface Finishes Conference pertaining to immersion gold or palladium might be very useful. Dave Anderson Medtronic.com As always, opinions are my own, and may not reflect the opinions of my employer. >>> "Chan, Marcelo" <[log in to unmask]> 04/22/98 09:55am >>> Can anyone describe to me how they would do such a PWB in terms of processing order and PWB finish selection? The application is RF and perhaps higher frequencies, which means that we may use materials ranging from Arlon 25N, rogers 4003 all the way to the traditional Rogers 6002..few layers...ratio of solderable pads to bondable is about 7 to 1 with about 100 pads on the whole board...1 by 1.5" in size... Are immersion Au, electrolytic Au, fused solder or Hasl viable options? thanks, Marcelo ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################